PCRE 函数
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PHP手册

preg_replace_callback

(PHP 4 >= 4.0.5, PHP 5)

preg_replace_callback — 执行一个正则表达式搜索并且使用一个回调进行替换

说明

mixed preg_replace_callback ( mixed $pattern , callback $callback , mixed $subject [, int $limit = -1 [, int &$count ]] )

这个函数的行为除了 可以指定一个callback替代replacement进行替换 字符串的计算, 其他方面等同于preg_replace()

参数

pattern

要搜索的模式, 可以使字符串或一个字符串数组.

callback

一个回调函数, 在每次需要替换时调用, 调用时函数得到的参数是从subject 中匹配到的结果. 回调函数返回真正参与替换的字符串.

你可能经常会需要callback函数而 仅用于preg_replace_callback()一个地方的调用. 在这种情况下, 你可以 使用匿名函数来定义一个匿名函数作 为preg_replace_callback()调用时的回调. 这样做你可以保留所有 调用信息在同一个位置并且不会因为一个不在任何其他地方使用的回调函数名称而污染函数名称空间.

Example #1 preg_replace_callback()和 create_function()

<?php
/* 一个unix样式的命令行过滤器, 用于将段落开始部分的大写字母转换为小写. */
$fp = fopen("php://stdin", "r") or die("can't read stdin");
while (!feof($fp)) {
    $line = fgets($fp);
    $line = preg_replace_callback(
        '|<p>\s*\w|',
        create_function(
            // single quotes are essential here,
            // or alternative escape all $ as \$
            '$matches',
            'return strtolower($matches[0]);'
        ),
        $line
    );
    echo $line;
}
fclose($fp);
?>

subject

要搜索替换的目标字符串或字符串数组.

limit

对于每个模式用于每个subject字符串的最大可替换次数. 默认是-1(无限制).

count

如果指定, 这个变量将被填充为替换执行的次数.

返回值

如果subject是一个数组, preg_replace_callback()返回一个数组, 其他情况返回字符串. 错误发生时返回NULL.

如果查找到了匹配, 返回替换后的 目标字符串(或字符串数组), 其他情况subject 将会无变化返回.

更新日志

版本 说明
5.1.0 增加了参数count.

范例

Example #2 preg_replace_callback()示例

<?php
// 将文本中的年份增加一年.
$text = "April fools day is 04/01/2002\n";
$text.= "Last christmas was 12/24/2001\n";
// 回调函数
function next_year($matches)
{
  // 通常: $matches[0]是完成的匹配
  // $matches[1]是第一个捕获子组的匹配
  // 以此类推
  return $matches[1].($matches[2]+1);
}
echo preg_replace_callback(
            "|(\d{2}/\d{2}/)(\d{4})|",
            "next_year",
            $text);

?>

以上例程会输出：

April fools day is 04/01/2003
Last christmas was 12/24/2002

Example #3 preg_replace_callback()使用递归构造处理BB码的封装

<?php
$input = "plain [indent] deep [indent] deeper [/indent] deep [/indent] plain";

function parseTagsRecursive($input)
{
    /* 译注: 对此正则表达式分段分析
     * 首尾两个#是正则分隔符
     * \[indent] 匹配一个原文的[indent]
     * ((?:[^[]|\[(?!/?indent])|(?R))+)分析:
     *         (?:[^[]|\[(?!/?indent])分析:
     *             首先它是一个非捕获子组
     *             两个可选路径, 一个是非[字符, 另一个是[字符但后面紧跟着不是/indent或indent.
     *         (?R) 正则表达式递归
     *     \[/indent] 匹配结束的[/indent]
     * /
    $regex = '#\[indent]((?:[^[]|\[(?!/?indent])|(?R))+)\[/indent]#';

    if (is_array($input)) {
        $input = '<div style="margin-left: 10px">'.$input[1].'</div>';
    }

    return preg_replace_callback($regex, 'parseTagsRecursive', $input);
}

$output = parseTagsRecursive($input);

echo $output;
?>

参见

PCRE 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: 执行一个正则表达式搜索并且使用一个回调进行替换

用户评论:

dvb (02-Mar-2012 06:40)

Simple function to remove a SHOUT in an input text.
Input: "This is so AWESOME!"
Output: "This is so awesome!"

<?php
function remove_shout($_text,$_max_caps=3)
{
    return preg_replace_callback('/[A-Z]{$_max_caps,}/',create_function('$matches','return strtolower($matches[0]);'),$_text);
}
?>

Florian Arndt (26-Jan-2012 08:26)

This small class allows PHP users to read JSON files with include statements in them. For instance the include {{{ "relative/to/including.json" }}} is replaced by the content of the json file located at "relative/to/including.json".

<?php
    /**
     * Handles JSON files with includes
     * Purpose: handle bigger JSON files by featuring "includes"
     *
     * @author Florian Arndt
     */
    class JWI {
        /**
         * Parses a JSON file and returns its contents
         * @param String $filename
         */
        static function read($filename) {
            if(!file_exists($filename))
                throw new Exception('<b>JWI Error: JSON file <tt>'.$filename.'</tt> not found!</b>');
            $content = join('', file($filename));
            $dir = dirname($filename);
            /**
             * replace
             *   include statements
             * with
             *   content of the file to include
             * recursively
             */
            $content = preg_replace_callback(
                '/{{{\s*"\s*(.+)\s*"\s*}}}/', // >include file< - pattern
                create_function(
                    '$matches', // callback parameter
                    sprintf(
                        '$fn = "%s/".$matches[1];'.
                        'return JWI::read($fn);',
                        realpath(dirname($filename))
                    )
                ),
                $content
            );
            return $content;
        }
    }

henzeberkheij at gmail dot com (23-Nov-2011 04:23)

also note that when you are using this functionality in a class and you need variables in that class, you can use a non static function as callback. array($this, functionName) should be enough to call an function of the class.

Either use create_function if you require the code only once,
use a static class function if no need for accessing variables in that class. or use the array metioned earlier in my post for having access to class variables or other functions!

webmaster at mp3s dot pl (28-Jul-2011 08:57)

I noticed that 'e' modifier use addslashed on result

<?
function wyczysc_strongi($string) {
    if(mb_strlen($string,'UTF-8')>60) {
        return $string;
    } else {
        return '<strong>'.$string.'</strong>';
    }
}

$tresc = "<strong>fajna dupa's</strong>";

$tresc = preg_replace("/<strong>(.*?)<\/strong>/ie",'wyczysc_strongi("$1")',$tresc);

echo $tresc will give: <strong>fajna dupa\'s</strong>
?>

solution: $tresc = stripslashes($tresc);
after callback

aleksander at throw dot pl (10-Jan-2011 10:59)

I needed a simple code to tidy up a string. It simply had to upper-case letters after dot. Simple code to do so:

<?php
$string = preg_replace_callback(
'|(?:\.)(?:\s*)(\w{1})|Ui',
create_function('$matches', 'return ". ".strtoupper($matches[1]);'), ucfirst($string)
);
?>

<?php
$string = 'lorem ipsum dolor sit amet, consectetur adipiscing elit. sed ullamcorper diam eu lorem varius nec porta elit iaculis.';

echo preg_replace_callback(
'|(?:\.)(?:\s*)(\w{1})|Ui',
create_function('$matches', 'return ". ".strtoupper($matches[1]);'), ucfirst($string)
);
?>

Will output: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed ullamcorper diam eu lorem varius nec porta elit iaculis.

<?php
$string = 'lorem ipsum dolor sit amet, consectetur adipiscing elit.                 sed ullamcorper diam eu lorem varius nec porta elit iaculis.';

echo preg_replace_callback(
'|(?:\.)(?:\s*)(\w{1})|Ui',
create_function('$matches', 'return ". ".strtoupper($matches[1]);'), ucfirst($string)
);
?>

Will output: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed ullamcorper diam eu lorem varius nec porta elit iaculis.

Nothing fancy, but useful :)

alex dot cs00 at yahoo dot ca (06-Oct-2010 10:09)

Don't use this function to fetch BBCode, as explained. If you have some text that runs over 5000 chars (average), it will run out of its limit and makes you download the PHP page.

According to this, you should instead use something more advanced yet complex. You will need a function called "str_replace_once()" (search for it), one called "countWord()", the famous "after()", "before()", "between()".

str_replace_once does same as str_replace, but only replace first occurence. As for countWord, I guess you know how to count the number of a word occurence. As for after, before and between, this is a function that you may find easily somewhere on the site by a user. Else, you can do it.

The following function is able to do all blocks, supposing [code] and [/code], you might wish things between parents dont get parsed, including [code] if inside of another [code].

<?php
function prepareCode($code, $op, $end)
{
    $ix = 0;
    $iy = 0;
    $nbr_Op = countWord($op, $code);
    while($ix < $nbr_Op)
    {
        if(in_string($op, before($end, $code), false))
        {
            // The following piece of code replace the default [tag] by [tag:#]
            $code = str_replace_once($op, substr($op, 0, -1).':'.$ix.']', $code);
            $iy++;
        }
        elseif(in_string($end, before($op, $code), false))
        {
            $iy = $iy-1;
            $code = str_replace_once($end, substr($end, 0, -1).':'.($ix-1).']', $code);
            $ix = $ix-2;
        }
        $ix++;
    }
    while(in_string($end, $code))
    {
        $code = str_replace_once($end, substr($end, 0, -1).':'.($iy-1).']', $code);
        $iy=$iy-1;
    }

    $code = preg_replace('#\\'.substr($end, 0, 1).':-[0-9]\]#i', '', $code);
    if(in_string(substr($op, 0, -1).':0]', $code) && !in_string(substr($end, 0, -1).':0]', $code))
    {
        $code .= substr($end, 0, -1).":0]";
    }
    return $code;
}
?>

$code returns the whole text semi-formated. You only need to use it as :
$code = prepareCode($code="Your text", $op="[tag]" , $end="[/tag]");
Then just replace the parent tags :
str_replace("[tag:0]", "<tag>", $code);
str_replace("[/tag:0]", "</tag>", $code);
So at the end something like :
[

chris at ocproducts dot com (02-Jul-2010 03:39)

The pcre.backtrack_limit option (added in PHP 5.2) can trigger a NULL return, with no errors. The default pcre.backtrack_limit value is 100000. If you have a match that exceeds about half this limit it triggers a NULL response.
e.g. My limit was at 100000 but 500500 triggered a NULL response. I'm not running unicode but I *guess* PCRE runs in utf-16.

Anonymous (09-Jun-2010 08:01)

Created this to fetch the link and name of an anchor tag. I use this when cleaning an HTML email to text. Using regex for HTML is not recommended but for this purpose I see no issue with it. This is not designed to work for nested anchors.

A note to keep in mind:
I was primarily concerned with valid HTML so if attributes do no use ' or " to contain the values then this will need to be tweaked.
If you can edit this to work better, please let me know.
<?php
/**
 * Replaces anchor tags with text
 * - Will search string and replace all anchor tags with text (case insensitive)
 *
 * How it works:
 * - Searches string for an anchor tag, checks to make sure it matches the criteria
 *         Anchor search criteria:
 *             - 1 - <a (must have the start of the anchor tag )
 *             - 2 - Can have any number of spaces or other attributes before and after the href attribute
 *             - 3 - Must close the anchor tag
 *
 * - Once the check has passed it will then replace the anchor tag with the string replacement
 * - The string replacement can be customized
 *
 * Know issue:
 * - This will not work for anchors that do not use a ' or " to contain the attributes.
 *         (i.e.- <a href=http: //php.net>PHP.net</a> will not be replaced)
 */
function replaceAnchorsWithText($data) {
    /**
     * Had to modify $regex so it could post to the site... so I broke it into 6 parts.
     */
    $regex  = '/(<a\s*'; // Start of anchor tag
    $regex .= '(.*?)\s*'; // Any attributes or spaces that may or may not exist
    $regex .= 'href=[\'"]+?\s*(?P<link>\S+)\s*[\'"]+?'; // Grab the link
    $regex .= '\s*(.*?)\s*>\s*'; // Any attributes or spaces that may or may not exist before closing tag
    $regex .= '(?P<name>\S+)'; // Grab the name
    $regex .= '\s*<\/a>)/i'; // Any number of spaces between the closing anchor tag (case insensitive)
   
    if (is_array($data)) {
        // This is what will replace the link (modify to you liking)
        $data = "{$data['name']}({$data['link']})";
    }
    return preg_replace_callback($regex, 'replaceAnchorsWithText', $data);
}

$input  = 'Test 1: <a href="http: //php.net1">PHP.NET1</a>.<br />';
$input .= 'Test 2: <A name="test" HREF=\'HTTP: //PHP.NET2\' target="_blank">PHP.NET2</A>.<BR />';
$input .= 'Test 3: <a hRef=http: //php.net3>php.net3</a><br />';
$input .= 'This last line had nothing to do with any of this';

echo replaceAnchorsWithText($input).'<hr/>';
?>
Will output:
Test 1: PHP.NET1(http: //php.net1).
Test 2: PHP.NET2(HTTP: //PHP.NET2).
Test 3: php.net3 (is still an anchor)
This last line had nothing to do with any of this

Drake (22-Mar-2010 01:48)

The good version of the class PhpHex2Str
<?php
class PhpHex2Str
{
    private $strings;

    private static function x_hex2str($hex) {
        $hex = substr($hex[0], 1);
        $str = '';
        for($i=0;$i < strlen($hex);$i+=2) {
            $str.=chr(hexdec(substr($hex,$i,2)));
        }
        return $str;
    }

    public function decode($strings = null) {
        $this->strings = (string) $strings;
        return preg_replace_callback('#\%[a-zA-Z0-9]{2}#', 'PhpHex2Str::x_hex2str', $this->strings);
    }
}

// Exemple
$obj = new PhpHex2Str;

$strings = $obj->decode($strings);
var_dump($strings);
?>

Drake (21-Mar-2010 08:05)

Decode Hexa to Strings =)
<?php
class PhpHex2Str
{
    private $strings;

    private function x_hex2str($hex) {
        $hex = substr($hex[0], 1);
        $str = '';
        for($i=0;$i < strlen($hex);$i+=2) {
            $str.=chr(hexdec(substr($hex,$i,2)));
        }
        return $str;
    }

    public function decode($strings = null) {
        $this->strings = (string) $strings;
        return preg_replace_callback('#\%[a-zA-Z0-9]{2}#', 'x_hex2str', $this->strings);
    }
}

// Example
$strings = 'a %20 b%0A h %27 h %23';

$obj = new PhpHex2Str;
$strings = $obj->decode($strings);
var_dump($strings);
?>

Matt (14-Sep-2009 05:24)

If you're looking to show only the first digit and last four digits of a credit card number (4xxxxxxxxxxxx2331) use something like this:
preg_replace_callback('/((.)(.*))?(.{4})/', create_function('$x', 'return $x[2].str_repeat("x", strlen($x[3])).$x[4];'), '$CCNUMBER')

ixiter at gmail dot com (29-Jul-2009 03:06)

When you use preg_replace_callback in a class and have the callback function as a private method of that class, you need to set the callback function name like className::CallBack.
self::CallBack does not work and returns an error:
"Cannot call method self::CallBack() or method does not exist"!

<?php
class myClass{
    public function parsetext($text){
        // parses text and sets literals A - C to lower case
        // this works
        return preg_replace_callback('|([a-c])|i', 'myClass::preg_tolower', $text);
    }
    public function parsefail($text){
        // parses text and sets literals A - C to lower case
        // this fails
        return preg_replace_callback('|([a-c])|i', 'self::preg_tolower', $text);
    }
   
    private static function preg_tolower($matches){
        return strtolower($matches[1]);
    }
}

$parser = new myClass;
echo $parser->parsetext('ABCDEFGH');
// echoes abcDEFGH

echo $parser->parsefail('ABCDEFGH');
// throws the error
?>

carlos dot ballesteros at softonic dot com (02-Jul-2009 04:02)

A simple function to replace a list of complete words or terms in a string (for PHP 5.3 or above because of the closure):

<?php
function replace_words($list, $line, $callback) {
    return preg_replace_callback(
        '/(^|[^\\w\\-])(' . implode('|', array_map('preg_quote', $list)) . ')($|[^\\w\\-])/mi',
        function($v) use ($callback) { return $v[1] . $callback($v[2]) . $v[3]; },
        $line
    );
}
?>

Example of usage:
<?php
$list = array('php', 'apache web server');
$str = "php and the apache web server work fine together. php-gtk, for example, won't match. apache web servers shouldn't too.";

echo replace_words($list, $str, function($v) {
    return "<strong>{$v}</strong>";
});
?>

chris AT cmbuckley DOT co DOT uk (09-Jun-2009 03:44)

This function does not support named subpatterns, so you can't do

<?php

preg_replace_callback('/(?<char>[a-z])/', 'callback', 'word');

function callback($matches) {
    var_dump($matches);
}

?>

and expect to get $matches['char'] in your function.

mariush (12-May-2009 09:17)

If you're planning to use preg_replace_callback inside a class, you need to use the array() function:

<?php
class MyClass
{

  function preg_callback_url($matches)
  {
    //var_dump($matches);
    $url = $matches[1].$matches[2];
    $text = '';
    $pos = strpos($url,' ');
    if ($pos!==FALSE) {
      $text = trim(substr($url,$pos+1));
      $url = substr($url,0,$pos);
    }
    return '<a href="'.$url.'" rel="nofollow">'.(($text!='') ? $text : $url).'</a>';
  }

  function ParseText($text)
  {
    return preg_replace_callback('/\[(http|https|ftp)(.*?)\]/iS',array( &$this, 'preg_callback_url'), $text);
  }

}
?>

james dot records at gmail dot com (26-Apr-2009 08:22)

This is what i use to read log files and do dns lookups on the ip's from the file.

<?php
function resolve_logs($arr) {
        return gethostbyaddr($arr[0]);
}

$logent=file('yourlogfile');

$ipaddr = '/\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}/';
$logent = preg_replace_callback($ipaddr, resolve_logs, $logent);
?>

long2hu3 ATT yahoo DOTT com (02-Apr-2009 07:25)

When you access variables from outside in a callback function, use the $global keyword:

<?php

// global # 1:
global $x;

$x = 0;
$str = '&Bla bla. &#x25ba;';

$find = '/(\&)([^#])/';

// global # 2:
$replace = create_function('$f',
    'global $x; $x ++; return $f[2];';

$str2 = preg_replace_callback($find, $replace, $str);

// $x == 1
// $str2 == 'Bla bla. &#x25ba;'
// without global, $x would be 0

?>

tijn at q-go dot com (06-Jan-2009 10:01)

To access a local variable within a callback, use currying (delayed argument binding). For example
<?php
function curry($func, $arity) {
    return create_function('', "
        \$args = func_get_args();
        if(count(\$args) >= $arity)
            return call_user_func_array('$func', \$args);
        \$args = var_export(\$args, 1);
        return create_function('','
            \$a = func_get_args();
            \$z = ' . \$args . ';
            \$a = array_merge(\$z,\$a);
            return call_user_func_array(\'$func\', \$a);
        ');
    ");
}

function on_match($transformation, $matches)
{
    return $transformation[strtolower($matches[1])];
}

$transform = array('a' => 'Well,', 'd'=>'whatever', 'b'=>' ');

$callback = curry(on_match, 2);
echo preg_replace_callback('/([a-z])/i', $callback($transform), 'Abcd');

echo "\n";
?>

outputs:

"Well, whatever"

The magic lies in this curry function I found here: http://www.sitepoint.com/forums/showthread.php?threadid=336758

tijn at q-go dot com (05-Jan-2009 04:48)

To access a local variable within a callback, use currying (delayed argument binding). For example
<?php
function curry($func, $arity) {
    return create_function('', "
        \$args = func_get_args();
        if(count(\$args) >= $arity)
            return call_user_func_array('$func', \$args);
        \$args = var_export(\$args, 1);
        return create_function('','
            \$a = func_get_args();
            \$z = ' . \$args . ';
            \$a = array_merge(\$z,\$a);
            return call_user_func_array(\'$func\', \$a);
        ');
    ");
}

function on_match($transformation, $matches)
{
    return $transformation[strtolower($matches[1])];
}

$transform = array('a' => 'Well,', 'd'=>'whatever', 'b'=>' ');

$callback = curry(on_match, 2);
echo preg_replace_callback('/([a-z])/i', $callback($transform), 'Abcd');

echo "\n";
?>

outputs:

"Well, whatever"

The magic lies in this curry function I found here: http://www.sitepoint.com/forums/showthread.php?threadid=336758

nicolaspar at gmail dot com (20-Dec-2008 02:33)

To spend more than one parameter can do the following (note the "e" parameter in preg_replace function)
<?
$array = array(
1=>'ONE',
2=>'TWO',
3=>'Three'
);

function search(&$array, $str, $foo, $bar){
    return ( empty($array[$str]) ? '['.$foo.'-'.$bar.']' : $array[$str] );
}

function keys(&$array, $str,$foo,$bar){
    return preg_replace('/\[(.*?)\]/e',"search(\$array,$1,\$foo,\$bar)",$str);
}

$str = "One [1] Two [2] Three [3], Other parameter [22]";

echo keys($array, $str,'Foo','Bar');
?>
Nice

nene at triin dot net (20-May-2008 11:14)

The first example is bad, because it creates function for every line it processes. When the file has many lines, you could easily run out of memory. The code should be changed so, that create_function() is used outside of loop.

Sjon at hortensius dot net (24-Jun-2007 12:56)

preg_replace_callback returns NULL when pcre.backtrack_limit is reached; this sometimes occurs faster then you might expect. No error is raised either; so don't forget to check for NULL yourself

matt at mattsoft dot net (26-Apr-2006 10:16)

it is much better on preformance and better practice to use the preg_replace_callback function instead of preg_replace with the e modifier.

function a($text){return($text);}

// 2.76 seconds to run 50000 times
preg_replace("/\{(.*?)\}/e","a('\\1','\\2','\\3',\$b)",$a);

// 0.97 seconds to run 50000 times
preg_replace_callback("/\{(.*?)\}/s","a",$a);